In such an X-ray equipment, between the X-ray tube and the X-ray detector, for the purpose of regulating the X-ray radiation field, which is an irradiation range of the X-ray irradiated from the X-ray tube with respect to a subject, a collimator which is an X-ray diaphragm mechanism including a plurality of collimator leaves arranged in an openable and closable manner in the radiation range of the X-ray irradiated from the X-ray tube is installed. When adjusting the X-ray radiation field to be irradiated from the X-ray tube toward the subject using the collimator, a visible light source called a collimator lamp installed in the collimator on the opposite side of the object is turned on to form a radiation field of visible light so that the radiation field of the visible light can be visually recognized. Thus, the X-ray radiation field to be adjusted by the collimator mechanism is confirmed (see Japanese Patent Application Publication No. 2001-70292 (hereinafter referred to as “Patent Document 1”); and Japanese Patent Application Publication No. 2013-215495 (hereinafter referred to as “Patent Document 2”).
As a visible light source for such a collimator, conventionally, a halogen lamp has been used. A halogen lamp has a problem that the power consumption is large. In addition, there also is a problem that a halogen lamp is relatively short in lifetime, which requires regular replacement.
For this reason, a light source device for a collimator has been proposed in which an LED for irradiating visible light is used as a light source (see Japanese Patent Application Publication No. 2004-209259 (hereinafter referred to as “Patent Document 3”)). In the light source device for a collimator described in Patent Document 3, in order to improve the illuminance ratio (edge contrast) between the radiation field by the visible light and the outer circumference region of the radiation field, it is configured such that LEDs are arranged inside a cone of a compound parabolic condenser (CPC) shape.
In the light source device for a collimator described in the aforementioned Patent Document 3, since all of visible lights irradiated from the LEDs are condensed by the reflecting surface, the illuminance in the visible light radiation field is improved. However, visible lights directed in all directions are condensed, which in turn causes a difficulty in obtaining an illuminance ratio exceeding a certain level. In the light source device for a collimator described in Patent Document 3, as described in Patent Document 3, the illuminance ratio between a region inside from the edge of the radiation field of the visible light by 3 mm and a region outside from the edge of the radiation field of the visible light by 3 mm is only about 1.458 or 1.923.